1. Field of the invention
The present invention relates to a method of and an apparatus for reproducing signals recorded on a magnetic recording medium, and more particularly to a method of and an apparatus for reproducing magnetically recorded signals by employing a ring-shaped head made of a metallic magnetic material such as sendust, permalloy, amorphous material, or the like as a field-responsive playback head in longitudinal magnetization recording, or by employing such a ring-shaped head, a secondary magnetic excitation pole of the metallic magnetic material, or a primary magnetic excitation pole of the metallic magnetic material as a field-responsive playback head in perpendicular magnetization recording.
2. Description of the Prior Art
Various efforts have been made to accomplish higher packing densities on magnetic recording mediums. In magnetically recording signals with higher packing densities, it is preferable to lower the relative speed of movement between the recording medium and the magnetic head. Where magnetically recorded signals, particularly digital signals, are reproduced by a magnetic-induction-type playback head, the level of the reproduced signals is directly proportional to the speed of travel of the recording medium with respect to the magnetic head. Therefore, so long as the magnetic-induction-type playback head is employed, the relative speed of movement between the recording medium and the magnetic head cannot be reduced beyond a certain speed, resulting in a limitation on packing densities. In view of the difficulty of the magnetic-induction-type playback head, the tendency in high packing density magnetic recording is toward the use of a field-responsive magnetic head capable of generating reproduced signals at a level which is in direct proportion to the level of the magnetic field induced by the recorded signals irrespectively of the relative speed between the recording medium and the head and the track width.
One typical field-responsive head is a magneto-resistive-effect head (hereinafter referred to as an "MR head"). Since the MR head has been designed solely as a playback head, it has been manufactured independently of bulk heads or thin-film heads for magnetic recording. The fabrication of the MR head has required a complex process such as photolithography or other microscopic pattern formation techniques, and hence has resulted in increased cost. Another problem is that the signals reproduced by the MR head are subject to variations in voltage due to temperature changes.